The present invention relates in general to an acoustic sensor, and more particularly, to an acoustic sensor used in windy environments found on aircraft, moving ground vehicles, wind tunnels and in naturally windy conditions.
Signal detection afforded by acoustic sensors or microphones are limited in windy conditions by at least two distinct forms of wind-induced noise. The first form is due to disturbances in the wind created by the acoustic sensor, which is solely caused by interaction of the wind and the aerodynamics of the sensor and/or sensor windscreen. The second form of wind-induced noise involves complex velocity and pressure fluctuations that are an inherent component of most wind.
The solution of the first form of wind-induced noise is proper aerodynamics. Proper aerodynamics design seeks to minimally disturb the wind, avoid separation of flow from the surface of the windscreen and thereby prevent unsteady, noisy flow from developing. Various distinct design techniques have been proposed for achieving proper aerodynamics. However, the low-noise achievement of these design techniques has been limited to the condition that winds are approaching in a given direction. That is, when winds alter their course, the low-noise performance of these aerodynamic design techniques is negated.
The second form of wind-induced noise caused by complex velocity and pressure fluctuations inherent to most winds is more difficult to address. Currently, foams, fabrics and other porous materials have been used to lessen the effects of these natural fluctuations on the acoustic sensors. The most common of these techniques is the use of an open cell, reticulated foam ball. However, all such approaches only offer limited immunity to inherent wind fluctuations, and are not sufficiently rugged for many applications.